Oil-based ink composition for ink-jet recording

ABSTRACT

The present invention provides an oil-based ink composition for ink-jet recording comprising at least a coloring material, an organic solvent and a non-aqueous resin emulsion.

FIELD OF THE INVENTION

The present invention relates to an oil-based ink composition forink-jet recording. More particularly, it relates to an oil-based inkcomposition having excellent image quality and fixability which containspolymer resin fine particles.

BACKGROUND OF THE INVENTION

Various ink-jet recording methods such as a method of discharging an inkby utilizing electrostatic attracting force (electric-field controllingmethod), a method of discharging an ink by utilizing driving pressure ofa piezoelectric element (drop-on-demand method or pressure pulsemethod), and a method of discharging an ink by utilizing pressuregenerated by forming gas bubbles with high heat and growing the same(bubble or thermal jet method) are known as an ink-jet recording method.An extremely high definition image can be obtained by those methods.Furthermore, in those ink-jet recording methods, a water-based ink usingwater as the main solvent and an oil-based ink using an organic solventas the main solvent are generally used.

A printed image obtained using a water-based ink is generally poor inwater resistance, and it is difficult to print an image on a recordingmedium having water-resistant surface. Contrary to this, an oil-basedink has various advantages such that it can provide a printed imagehaving excellent water resistance, and additionally, it facilitatesprinting on a recording medium having water-resistant surface and ahigh-quality paper. Furthermore, an oil-based ink using a pigment as acoloring material has excellent light resistance. Even though thoseadvantages, further improvement in properties such as fixability,durability, wear resistance and curability has been desired with theexpansion of applications of the oil-based ink. In particular, where thecoloring material is white, further improvement in properties such asfixability, durability, wear resistance and curability is desired, inaddition to improvement of image in terms of whiteness and shieldingproperty.

A technique in which a resin which dissolves in a solvent is used andthe resin bonds and fixes a pigment and a recording medium at the timewhen the solvent is dried, is disclosed as a method of increasingfixability of a pigment to a recording medium (for example, see PatentDocument 1). The larger the molecular weight of the resin whichdissolves in a solvent, the more excellent the fixability and strengthwhen dried, but this is accompanied with a great increase of theviscosity of an ink composition. As a result, discharge property of anink composition is decreased, and in an extreme case, a nozzle isclogged and an ink composition cannot be discharged. A resin having alow molecular weight can suppress the increase of viscosity, butfixability and strength of an ink composition are decreased.Additionally, where the amount of a resin present in a solvent in adissolved state is excess, it induces discharge defects such as flightdeflection and scattering, regardless of a molecular weight of a resin.

In view of the above, a technique of adding an emulsion or a suspension,having resin fine particles dispersed in a dispersion medium(hereinafter simply referred to as a “resin emulsion” withoutdistinguishing an emulsion and a suspension), to an ink composition isproposed (for example, see Patent Documents 2 to 5). However, unlike awater-based ink composition comprising water as the main component, anoil-based ink composition greatly changes its properties depending onthe kind of a solvent used. Therefore, it is necessary to appropriatelyselect a resin emulsion suitable to the kind of a resin emulsion and adispersion medium used.

Patent Document 1: WO02/100652

Patent Document 2: JP-A-2004-250659

Patent Document 3: JP-A-2005-23299

Patent Document 4: JP-A-2005-290362

Patent Document 5: JP-A-2005-314655

SUMMARY OF THE INVENTION

The present invention has an object to provide an oil-based inkcomposition for ink-jet recording, which suppresses a viscosityincrease, has excellent discharge property and fixability to a recordingmedium, and provides a printed matter having good image quality.

As a result of extensive and intensive investigations, the presentinventors have found that good fixability and good image quality areobtained by using an oil-based ink composition comprising at least:

(1) an alkyl glycol ether solvent having excellent ink jet properties,and

(2) a polyacryl polyol resin emulsion (non-aqueous resin emulsion) inwhich a dispersion medium comprises an aliphatic hydrocarbon compoundand/or an alicyclic hydrocarbon compound which are/or is a petroleumsolvent.

The present invention has been achieved based on this finding.

It has been further found that where the above oil-based ink compositionis a white ink, an image quality having excellent high whiteness andhigh shielding property, and good fixability are obtained by containinga white hollow resin emulsion as a coloring material.

That is, the above object can be achieved by the followingconstitutions.

(1) An oil-based ink composition for ink-jet recording comprising atleast a coloring material, an organic solvent and a non-aqueous resinemulsion.

(2) The oil-based ink composition for ink-jet recording as described in(1) above, wherein a resin constituting the non-aqueous resin emulsionis a polyacryl polyol resin.

(3) The oil-based ink composition for ink-jet recording as described in(1) or (2) above, wherein a dispersion medium of the non-aqueous resinemulsion is an aliphatic hydrocarbon and/or an alicyclic hydrocarbon.

(4) The oil-based ink composition for ink-jet recording as described in(3) above, wherein the aliphatic hydrocarbon is a linear alkane and/or abranched alkane.

(5) The oil-based ink composition for ink-jet recording as described in(3) above, wherein the alicyclic hydrocarbon is an alkyl cyclohexane.

(6) The oil-based ink composition for ink-jet recording as described inany one of (1) to (5) above, which is a white ink wherein the coloringmaterial contains a hollow resin emulsion.

(7) The oil-based ink composition for ink-jet recording as described in(6) above, wherein the hollow resin emulsion contains hollow resinparticles which are fine particles having an average particle size offrom 0.3 to 1.0 μm.

(8) The oil-based ink composition for ink-jet recording as described in(6) or (7) above, wherein the hollow resin emulsion contains hollowresin particles in an amount of from 0.5 to 25% by weight based on theweight of the whole ink composition.

According to the present invention, a non-aqueous oil-based inkcomposition having excellent image quality and fixability can beprovided.

DETAILED DESCRIPTION OF THE INVENTION

The ink composition of the present invention is an oil-based inkcomposition for ink-jet recording comprising at least a coloringmaterial, an organic solvent and a non-aqueous resin emulsion.

In the oil-based ink composition of the invention, the coloring materialcan use pigments and/or dyes generally used in the conventionaloil-based ink composition.

Those pigments and/or dyes can be used alone or as mixtures of two ormore thereof.

The pigment can use inorganic pigments or organic pigments. Specificexamples of the pigment that can be used include carbon black, cadmiumred, molybdenum red, chromium yellow, cadmium yellow, titanium yellow,chromium oxide, pyridiane, titanium cobalt green, ultramarine blue,Prussian blue, cobalt blue, diketopyrrolopyrrole, anthraquinone,benzimidazolone, anthrapyrimidine, azo pigment, phthalocyanine pigment,quinacridone pigment, isoindolinone pigment, dioxadine pigment, surenepigment, perylene pigment, perynone pigment, thioindigo pigment,quinophthalone pigment and metal complex pigment.

An average particle size of the above pigment particles is notparticularly limited, but is preferably from 50 to 500 nm.

Examples of the dye that can be used include azo dye, metal complex saltdye, naphthol dye, anthraquinone dye, indigo dye, carbonium dye,quinoneimine dye, xanthene dye, cyanine dye, quinoline dye, nitro dye,nitroso dye, benzoquinone dye, naphthoquinone dye, phthalocyanine dyeand metal phthalocyanine dye. An oil-soluble dye is particularlypreferred.

In the oil-based ink composition of the invention, the content of thecoloring material can appropriately be selected according toapplications and printing properties, but is preferably from 0.5 to 25%by weight, more preferably from 0.5 to 15% by weight, and mostpreferably from 1 to 10% by weight, based on the weight of the whole inkcomposition.

The oil-based ink composition of the invention preferably contains ahollow resin emulsion as the coloring material.

The hollow resin emulsion in the invention is an oil-based dispersion ofhollow resin fine particles, and the hollow resin fine particle ispreferably a white coloring material. The hollow resin fine particle hasa particle size of preferably from 0.3 to 1.0 μm.

The hollow resin particles can use the same particles as the hollowresin fine particles described in Japanese Patent Application No.2006-061511.

Preparation method of the hollow resin fine particles used in theinvention is not particularly limited, and can use various conventionalmethods. The preparation method is described in, for example, U.S. Pat.No. 4,880,465, JP-A-2003-313481, and U.S. Pat. Nos. 5,229,209,4,594,363, 4,427,836 and 4,089,800. Furthermore, various hollow resinfine particles are commercially available. The preparation method of thehollow resin fine particles, and design method of pore size or outerdiameter are also conventional, and are described in, for example, theabove-described references. The hollow resin fine particles aretypically prepared according to the general emulsion polymerizationtechnique. Furthermore, the hollow resin fine particles can be preparedas a stable dispersion system comprising the individual hollow fineparticle dispersed in an organic solution medium (describedhereinafter). The dispersion thus obtained has good dispersibilityimparted thereto, without requiring pulverization operation and grindingoperation that are required in preparing the general pigment inkcomposition, and can be utilized in, for example, preparation of an inkcomposition for ink-jet recording.

Vinyl monomer that can be used in preparation of the hollow resin fineparticles can include nonionic monoethylenically unsaturated monomers,and examples thereof include styrene, vinyltoluene, ethylene, vinylacetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, and various esters of (meth)acrylic acid such as methyl acrylate(MA), methyl methacrylate (MMA), ethyl acrylate (EA) or butyl acrylate(BA), for example, (C1-C20) alkyl or (C3-C20) alkenyl esters. Examplesof the (meth)acrylic acid ester that can be used include acryl esterssuch as methyl methacrylate (MMA), methyl acrylate (MA), ethyl(meth)acrylate (EMA), butyl (meth)acrylate (BMA), 2-hydroxyethylmethacrylate (HEMA), 2-ethylhexyl (meth)acrylate (EHMA), benzyl(meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl(meth)acrylate or stearyl (meth)acrylate.

A bifunctional vinyl monomer such as divinyl benzene, acrylmethacrylate, ethylene glycol dimethacryalte, 1,3-butane-dioldimethacrylate, diethylene glycol dimethacrylate or trimethylolpropanetrimethacryate can be copolymerized to crosslink, thereby forming anouter shell (resin film).

The hollow resin emulsion according to the invention can be prepared asa dispersion system comprising the hollow resin fine particles dispersedin an organic solution medium. The organic solution medium that canpreferably be used include polar organic solvents such as alcohols(methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropylalcohol, fluorinated alcohol and the like), ketones (acetone, methylethyl ketone, cyclohexanone and the like), carboxylic acid esters(methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methylpropionate, ethyl propionate and the like), and ethers (diethyl ether,dipropyl ether, tetrahydrofuran, dioxane and the like).

More preferred organic solution medium includes a mixture of adiethylene glycol compound which is liquid at ordinary temperature underordinary pressure, and a dipropylene glycol compound which is liquid atordinary temperature under ordinary pressure, as described inWO2002/055619. Specifically, diethylene glycol diethyl ether anddipropylene glycol monoethyl ether can be used in combination.Furthermore, triethylene glycol monomethyl ether, triethylene glycoldimethyl ether, triethylene glycol monobutyl ether, tetraethylenedimethyl ether, tetraethylene monobutyl ether and the like can be used.

When the hollow resin emulsion is used as the coloring material, thecontent of the hollow resin fine particles in the hollow resin emulsionis preferably from 0.5 to 25% by weight, and more preferably from 5 to25% by weight, based on the weight of the whole ink composition.

The oil-based ink composition of the invention contains the non-aqueousresin emulsion.

Even thought the non-aqueous resin emulsion (non-aqueous polymer resinfine particles are dispersed) used in the invention is added to an inkcomposition, the resin fine particles are insoluble, and therefore,remarkable viscosity increase as in the case of adding a soluble polymercompound is not induced. As a result, deterioration of dischargeproperty due to resin addition can be suppressed.

The resin (non-aqueous polymer resin) constituting the non-aqueous resinemulsion is not particularly limited. However, urethane and acrylicresins are preferred, and a polyacryl polyol resin is more preferred.

Dispersion medium of the non-aqueous resin emulsion is not particularlylimited. However, an aliphatic hydrocarbon or an alicyclic hydrocarbonalone or a mixture of those is preferred, and the mixture of those ismore preferred.

The aliphatic hydrocarbon is preferably a linear alkane or a branchedalkane. Those may be used alone or mixtures of two or more thereof.

The linear alkane is preferably an alkane having from 5 to 15 carbonatoms, and examples thereof include n-pentane, n-hexane, n-heptane,n-octane, n-nonane, n-decane and n-undecane. The branched alkane ispreferably an alkane having from 5 to 15 carbon atoms, and examplesthereof include 2,3-dimethylbutane, 2-methylhexane, 3-methylheptane,3-methylhexane and 2,3-dimethylpentane.

The alicyclic hydrocarbon is preferably an aliphatic hydrocarbon havingfrom 5 to 15 carbon atoms. Cyclopentane, cyclohexane, cycloheptane,cyclooctane and compounds in which hydrogen in those compounds issubstituted with an alkyl group are preferred, and an alkyl cyclohexanein which hydrogen in cyclohexane is substituted with an alkyl group ismore preferred.

Petroleum solvents generally widely used contain benzene, toluene andxylene that are harmful, and use of such solvents is not preferred fromthe standpoint of environment. From this point, it is preferred to use amixed solvent comprising the above-described aliphatic hydrocarboncompounds and alicyclic hydrocarbon compounds.

The resin emulsion dispersed with a dispersion medium is commerciallyavailable. For example, N-2043-AF-1 and N-2043-60MEX, products of HarimaChemicals, Inc., can be used as the emulsion of a polyacryl polyol(polyacryl polyol fixing resin), and SANPRENE IB-F370 and SAMPRENEIB-501, products of Sanyo Chemical Industries, Ltd., can be used as theemulsion of a urethane resin (polyurethane fixing resin).

N-2043-AF-1 described above is a resin emulsion in which a polyacrylpolyol resin is dispersed in a mixed solvent comprising C9 and C10 alkylcyclohexanes as the main component, and N-2043-60MEX described above isalso a polyacryl polyol resin. SANPRENE IB-F370 described above is aresin emulsion in which a urethane resin is dispersed in a solventcomprising propylene glycol monomethyl ether as the main component, andSANPRENE IB-501 is a resin emulsion in which a urethane resin isdispersed in a mixed solvent comprising ethyl acetate and isopropylalcohol.

The oil-based ink composition of the invention preferably contains atleast any one of an alkylene glycol compound that is liquid at ordinarytemperature under ordinary pressure and a lactone, as an organicsolvent, and more preferably contains the alkylene glycol compound as anorganic solvent.

The alkylene glycol compound is preferably an ethylene glycol compoundor a propylene glycol compound, as described in WO2002/055619.

Examples of the preferred ethylene glycol compound include ethyleneglycol, diethylene glycol, triethylene glycol, tetraethylene glycol, anda monoether or a diether of a polyethylene glycol, and a diethyleneglycol compound is more preferred.

Examples of the preferred propylene glycol compound include propyleneglycol, dipropylene glycol, tripropylene glycol, and a monother or adiether of a polypropylene glycol, and a dipropylene glycol compound ismore preferred.

The diethylene glycol compound can use, for example, a diethylene glycolcompound represented by the following general formula (I).R¹¹—O—C₂H₄—O—C₂H₄—O—R¹²  (I)wherein R¹¹ and R¹² each independently represent a hydrogen atom, analkyl group having from 1 to 4 carbon atoms or an R¹³CO group whereinR¹³ represents an alkyl group having from 1 to 4 carbon atoms.

The dipropylene glycol compound can use, for example, a dipropyleneglycol compound represented by the following general formula (II).R²¹—O—C₃H6—O—C₃H₆—O—R²²  (II)wherein R²¹ and R²² each independently represent a hydrogen atom, analkyl group having from 1 to 4 carbon atoms or an R²³CO group whereinR²³ represents an alkyl group having from 1 to 4 carbon atoms.

The term “alkyl group having from 1 to 4 carbon atoms” used herein meansa linear or branched alkyl group, and can be, for example, a methylgroup, an ethyl group, an n-propyl group, an iso-propyl group, ann-butyl group, an iso-butyl group, a sec-butyl group or a tert-butylgroup.

The lactone is preferably a lactone having 6 or less carbon atoms, andexamples of the preferred lactone include β-propiolactone,β-butyrolactone, γ-butyrolactone, γ-valerolactone and ε-caprolactone.

The diethylene glycol compound, dipropylene glycol compound and lactonethat can be used in the oil-based ink composition of the presentinvention each have a boiling point of preferably 150° C. or higher, andmore preferably 180° C. or higher, under ordinary pressure.

The diethylene glycol compound and dipropylene compound that can be usedin the oil-based ink composition of the invention each have a vaporpressure at 20° C. of preferably 1 hPa or lower, and more preferably 0.7hPa or lower. When the diethylene glycol compound and dipropylenecompound satisfying the above-described conditions of high boiling pointand low vapor pressure are used, load to provide local exhaustfacilities and exhaust gas treatment facilities is reduced, and thismakes it possible to improve working environment, and additionally, toreduce environmental load to ambient environment.

Examples of the preferred diethylene glycol compound that can be used inthe oil-based ink composition of the invention include diethyleneglycol; diethylene glycol ethers (particularly an alkyl ether) such asdiethylene glycol monomethyl ether, diethylene glycol dimethyl ether,diethylene glycol methylethyl ether, diethylene glycol monoethyl ether,diethylene glycol diethyl ether, diethylene glycol mono-n-butyl ether ordiethylene glycol di-n-butyl ether; and diethylene glycol esters such asdiethylene glycol monoethyl ether acetate, diethylene glycolmono-n-butyl ether acetate or diethylene glycol monoacetate. Of those,diethylene glycol, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, diethylene glycol diethyl ether, diethylene glycolmono-n-butyl ether, diethylene glycol di-n-butyl ether, diethyleneglycol monoethyl ether acetate and diethylene glycol monobutyl etheracetate are preferred.

Examples of the preferred dipropylene glycol compound that can be usedin the oil-based ink composition of the invention include dipropyleneglycol; and dipropylene glycol ethers (particularly an alkyl ether) suchas dipropylene glycol monomethyl ether or dipropylene glycol monoethylether.

The oil-based ink composition of the invention preferably contains thediethylene glycol compound, and the content thereof can appropriately beselected according to the printing properties, but is preferably from 20to 80% by weight based on the weight of the whole ink composition.

In addition to the diethylene glycol compound, the dipropylene glycolcompound, the lactone or their mixtures, the oil-based ink compositionof the invention can further contain a polyethylene glycol monoethercompound which is liquid at ordinary temperature under ordinary pressurerepresented by the following general formula (III) as an organicsolvent.R³¹—O—(C₂H₄—O)_(n)—H  (III)wherein R³¹ represents an alkyl group having from 1 to 6 carbon atoms(preferably, an alkyl group having from 1 to 4 carbon atoms), and n isan integer of from 3 to 6.

The term “alkyl group having from 1 to 6 carbon atoms” used herein meansa linear or branched alkyl group, and can be, for example, a linear orbranched pentyl group or a linear or branched hexyl group, in additionto the “alkyl group having from 1 to 4 carbon atoms” described before.

The polyethylene glycol monoether compound that can be used in theoil-based ink composition of the invention has a boiling point ofpreferably 200° C. or higher, and more preferably 250° C. or higher,under ordinary pressure. Furthermore, the polyethylene glycol monoethercompound that can be used in the oil-based ink composition of theinvention has a flash point of preferably 100° C. or higher, and morepreferably 130° C. or higher. When such a polyethylene glycol monoethercompound is used, volatilization inhibition property can be imparted tothe oil-based ink composition of the invention. For example, whenvolatilization of the ink composition is inhibited in a tube whichtransports an ink composition to a printer head from an ink cartridge,accumulation of a solid content can be prevented or reduced in the tube.

Examples of the preferred polyethylene glycol monoether compound includea triethylene glycol monoether compound (such as triethylene glycolmonomethyl ether or triethylene glycol monobutyl ether), and a mixtureof polyethylene glycol monoether compounds wherein n is from 4 to 6 inthe general formula (III), such as a mixture of tetraethylene glycolmonomethyl ether, pentaethylene glycol monomethyl ether and hexaethyleneglycol monomethyl ether.

The oil-based ink composition of the invention can further contain otherorganic solvents as the organic solvent, in addition to the diethyleneglycol compound, the dipropylene glycol compound, the lactone andoptionally the polyethylene glycol monoether compound.

Examples of the other organic solvent that can preferably be usedinclude polar organic solvents such as alcohols (such as methyl alcohol,ethyl alcohol, propyl alcohol, butyl alcohol or fluorinated alcohol),ketones (such as acetone, methyl ethyl ketone or cyclohexanone),carboxylic acid esters (such as methyl acetate, ethyl acetate, propylacetate, butyl acetate, methyl propionate or ethyl propionate), andethers (such as diethyl ether, dipropyl ether, tetrahydrofuran ordioxane).

Where the oil-based ink composition of the invention contains at leastany one of the diethylene glycol compound, dipropylene glycol compoundand the lactone, and does not contain the polyethylene glycol monoethercompound, the sum of the diethylene glycol compound, dipropylene glycolcompound and the lactone is preferably 75% by weight or more of thewhole organic solvent component.

Where the oil-based ink composition of the invention contains thepolyethylene glycol monoether compound in addition to the diethyleneglycol compound, the dipropylene glycol compound and the lactone, thesum of the diethylene glycol compound, the dipropylene glycol compound,the lactone and the polyethylene glycol monoether compound is preferably80% by weight or more of the whole organic solvent component.

The oil-based ink composition of the invention preferably contains apolyoxyethylene derivative which is a silicone surfactant or a nonionicsurfactant, other than the coloring material and the organic solvent.

The silicone surfactant that is preferably used is a polyester-modifiedsilicone or a polyether-modified silicone, and specific examples thereofinclude BYK-347, BYK-348, and BYK-UV 3500, 3510, 3530 and 3570 (allproducts of BYK-Chemie Japan). The polyoxyethylene derivative can use anacetylene glycol surfactant, and specific examples thereof includeSURFINOL 104, 82, 465, 485 AND TG (all trade names of Air Products andChemicals, Inc.), and OLFINE STG and OLFINE E1010 (all trade names ofNisshin Chemical Industry Co., Ltd.). Other commercially availableproducts include NISSAN NONION A-10R and A-13R (products of NOFCorporation), FLORENE TG-740W and D-90 (products of Kyoeisha ChemicalCo., Ltd.) and NOYGEN CX-100 (a product of Dai-Ichi Kogyo Seiyaku Co.,Ltd.).

The polyoxyethylene derivative is preferably a compound which is liquidat ordinary temperature under ordinary pressure. Examples of thepolyoxyethylene derivative include polyoxyethylene alkyl ethers such asa polyoxyethylene cetyl ether (such as NISSAN NONION P-208, a product ofNOF Corporation), a polyixyethylene oleyl ether (such as NISSAN NONIONE-202S and E-205S, products of NOF Corporation) or a polyoxyethylenelauryl ether (such as EMULGEN 106 and 108, products of Kao Corporation);polyoxyethylene alkyl phenol ethers such as a polyoxyethylene octylphenol ether (such as NISSAN NONION HS-204.5, HS-206 and HS-208,products of NOF Corporation); sorbitan monoesters such as a sorbitanmonocaprylate (such as NISSAN NONION CP-08R, a product of NOFCorporation) or a sorbitan monolaurate (such as NISSAN NONION LP-20R, aproduct of NOF Corporation); polyoxyethylene sorbitan monoesters such asa polyoxyethylene sorbitan monostearate (such as NISSAN NONION OT-221, aproduct of NOF Corporation); polycarboxylic acid polymeric activators(FLORENE G-700, a product of Kyoeisha Chemical Co., Ltd.);polyoxyethylene higher polymeric activators (such as EMULGEN 707 and709, products of Kao Corporation); tetraglycerin oleates (such as POEMJ-4581, Riken Vitamin Co., Ltd.); nonyl phenol ethoxyates (such asADECATOL NP-620, NP-650, NO-660, NP-675, NP-683 and NP-686, products ofADEKA Corporation); aliphatic phosphoric acid esters (such as ADECATOLCS-141E and TS-230E, products of ADEKA Corporation); sorbitansesquioleates (such as SOLGEN 30, a product of Dai-Ichi Kogyo SeiyakuCo., Ltd.); sorbitan monooleates (such as SOLGEN 40, a product ofDai-Ichi Kogyo Seiyaku Co., Ltd.); polyethylene glycol sorbitanmonolaurates (such as SOLGEN TW-20, a product of Dai-Ichi Kogyo SeiyakuCo., Ltd.); and polyethylene glycol sorbitan monooleates (such as SOLGENTW-80, a product of Dai-Ichi Kogyo Seiyaku Co., Ltd.). Furthermore, anacetylene glycol surfactant can be used as the polyoxyethylenederivative. The specific example of the preferred acetylene glycolsurfactant includes a compound represented by the following generalformula (IV).

wherein 0≦p+q≦50, and R⁴¹, R⁴² and R⁴³ each independently represent analkyl group, and preferably an alkyl group having from 1 to 6 carbonatoms.

Of the compounds represented by the above general formula (IV),particularly preferred compounds include2,4,7,9-tetramethyl-5-desine-4,7-diol, 3,6-dimethyl-4-octine-3,6-dioland 3,5-dimethyl-1-hexine-3-ol. Commercially available products can beused as the acetylene glycol surfactant represented by the generalformula (IV), and specific examples thereof include SURFINOL 104, 82,465, 485 and TG (all available from Air Products and Chemicals, Inc.),and OLFINE STG and OLFINE E1010 (all trade names of Nisshin ChemicalIndustry Co., Ltd.).

The polyoxyethylene derivative can use other commercially availableproducts, and specific examples thereof include NISSAN NONION A-10R andA-13R (products of NOF Corporation), FLORENE TG-740W and D-90 (productsof Kyoeisha Chemical Co., Ltd.), EMULGEN A-90 and A-60 (products of KaoCorporation) and NOYGEN CX-100 (a product of Dai-Ichi Kogyo Seiyaku Co.,Ltd.).

In the oil-based ink composition of the invention, the content of thepolyoxyethylene derivative can appropriately be selected according toresolubility to be imparted, but is preferably from 5 to 200 parts byweight, and more preferably from 30 to 120 parts by weight, per 100parts by weight of the content of the coloring material (particularly,pigment) in the ink composition.

The oil-based ink composition of the invention can contain a dispersant.The dispersant can use optional dispersants that are used in generaloil-based ink compositions, particularly oil-based ink compositions forink-jet recording. In particular, it is preferred to use a dispersantwhich effectively acts when a solubility parameter of an organic solventis from 8 to 11. Such a dispersant can use commercially availableproducts, and specific examples thereof include polyester-type polymercompounds (HINOACT KF1-M, T-6000, T-7000, T-8000, T-8350P and T-8000E,products of Takefu Fine Chemicals Co., Ltd.); SOLSPERSE 20000, 24000,32000, 32500, 33500, 34000 and 35200 (products of Avecia Limited);DISPER BYK-161, 162, 163, 164, 166, 180, 190, 191 and 192 (products ofBYK-Chemie, Japan); FLORENE DOPA-17, 22 and 33, and G-700 (products ofKyoeisha Chemical Co., Ltd.); AJISPER PB-821 and PB-711 (products ofAjinomoto Co., Inc.); and LP4010, LP4050, LP4055, and POLYMER 400, 401,402, 403, 450, 451 and 453 (products of EFKA Chemicals).

In the oil-based ink composition of the invention, the content of thedispersant can appropriately be selected depending on the coloringmaterial to be dispersed, but is preferably 5 to 200 parts by weight,and more preferably from 30 to 120 parts by weight, per 100 parts byweight of the content of the coloring material (particularly, pigment)in the ink composition.

The oil-based ink composition of the invention can contain otheradditives contained in general oil-based ink compositions, in additionto the above-described coloring material and organic solvent. Oneexample of such additives includes a stabilizer (for example, anantioxidant or an ultraviolet absorber). Examples of the antioxidantthat can be used include BHA (2,3-butyl-4-oxyanisole) and BHT(2,6-di-t-butyl-p-cresol), and examples of the ultraviolet absorber thatcan be used include a benzophenone compound and a benzotriazolecompound.

Viscosity of the oil-based ink composition of the invention can beadjusted by a binder resin. The viscosity (viscosity at a temperature of20° C.) of the oil-based ink composition of the invention is, forexample, 10 mPa·s, and preferably 5 mpa·s. Examples of the binder resinthat can be used include an acryl resin, a styrene acryl resin, arosin-modified resin, a phenolic resin, a terpene resin, a polyesterresin, a polyamide resin, an epoxy resin, a vinyl chloride-vinyl acetatecopolymer, a cellulose resin (such as cellulose acetate butyrate), and avinyl toluene-α-methylstyrene copolymer. The binder resin can act tofurther improve fixability of the coloring material to a recordingmedium according to the addition amount thereof.

The oil-based ink composition of the invention can be prepared by theconventional methods. When a pigment is used as the coloring material,the oil-based pigment ink composition can be obtained as follows. Apigment, a dispersant and a mixture (a part) of the above-describeddiethylene glycol compound and the above-described dipropylene glycolcompound are mixed, and a pigment dispersion is prepared using a ballmill, a bead mill, ultrasonic wave or a jet mill, followed by adjustingto have the desired ink properties. Subsequently, a binder resin, amixture (remainder) of the above-described diethylene glycol compoundand the above-described dipropylene glycol compound, and other additives(such as a dispersing agent or a viscosity regulator) are added understirring, thereby obtaining an oil-based pigment ink composition.Alternatively, a pigment and a dye are used together as the coloringmaterial, and an oil-based ink composition can be prepared by the samemethod as in the preparation method of the above oil-based pigment inkcomposition.

Properties of the oil-based ink composition of the invention are notparticularly limited. However, for example, the oil-based inkcomposition has surface tension of preferably from 20 to 50 mN/m. Wherethe surface tension is less than 20 mN/m, the ink compositionwet-expands on the surface of a printer head for ink-jet recording, oroozes thereon, and it may be difficult to discharge ink droplets. Wherethe surface tension exceeds 50 mN/m, the ink composition does notwet-expand on the surface of a recording medium, and good printing maynot be conducted.

The oil-based ink composition of the invention has the advantage thatthe ink composition is inert to a discharge nozzle surface having beensubjected to waste ink treatment. Therefore, the oil-based inkcomposition of the invention can advantageously be used to an ink-jetrecording method that discharges an ink from a printer head for ink-jetrecording having a discharge nozzle surface having been subjected towaste ink treatment. Furthermore, the oil-based ink composition of theinvention can prevent disadvantages in the case of using theconventional oil-based ink to a waste ink-treated head, specifically aphenomenon that an ink wet-expands on the waste ink-treated head, aphenomenon that ink discharging is unstable or a phenomenon that an inkcorrodes a head.

The oil-based ink composition of the invention is preferably used evenin utilization to an ink-jet recording head in which waste ink treatmenthas been subjected to a surface layer portion of a nozzle plate. By thecombination of the oil-based ink composition of the invention and anink-jet recording head to which waste ink treatment has been subjected,flight deflection of an ink is difficult to be generated, and good imagecan be recorded on a recording paper. According to the oil-based inkcomposition, surface state of a nozzle plate to which waste inktreatment has been subjected can be maintained in good state over a longperiod of time, and a long-term ink discharge stability can be realized.

The oil-based ink composition of the invention can be applied to variousink-jet recording methods. Specifically, the oil-based ink compositioncan be applied to various ink-jet recording methods such as anelectric-field controlling method in which an ink is dischargedutilizing electrostatic attracting force, a drop-on-demand method (orpressure pulse method) in which an ink is discharged utilizing drivingpressure of a piezoelectric element, and a bubble or thermal jet methodin which an ink is discharged by utilizing pressure caused by forminggas bubbles by high heat and growing the same. However, the oil-basedink composition of the invention is preferably applied to thedrop-on-demand method in which an ink is discharged utilizing drivingpressure of a piezoelectric element, and when printing is performed bythis method, discharge stability is excellent, high definition imagefree of color oozing and color bleeding can be obtained, andadditionally, wear resistance and water resistance are excellent.

Furthermore, when the oil-based ink composition of the invention isused, an excellent image can be formed on a large-sized recoding mediumof, for example, about A0 size by a large-sized ink-jet recordingdevice.

EXAMPLES

The present invention will be described in greater detail by referenceto the following Examples, but the invention should not be construed asbeing limited thereto.

Each color ink composition of the following Examples (1-1) to (1-5) andComparative Example (1-1) to (1-3), and each color ink composition incolor ink sets of Examples (1-6) to (1-9) were prepared as follows.

Preparation of pigment dispersion and preparation of color inkcomposition:

A mixture comprising 15 parts by weight of pigments shown below, 9 partsby weight of a dispersant (FLORENE DOPA-33, a product of KyoeishaChemical Co., Ltd.), and the remaining amount of diethylene glycoldiethyl ether was mixed and stirred for 1 hour using a dissolver,followed by conducting preliminary dispersion with a sand mill havingzirconia beads having a diameter of 2 mm filled therein. The preliminarydispersion was conducted until an average particle size of pigmentparticles was 5 μm or less. Subsequently, a pigment dispersion wasseparated with a separator, and dispersion treatment was conducted usinga sand mill having zirconia beads having a diameter of 0.3 mm filledtherein until the average particle size of the pigment particles was 200nm or less.

Pigment:

Pigment 1: C.I. Pigment Black 7

Pigment 2: C.I. Pigment Yellow 155

Pigment 3: C.I. Pigment Violet 19

Pigment 4: C.I. Pigment Blue 15:3

Pigment 5: C.I. Pigment Yellow 213

Using the pigment dispersion obtained, the following ink composition wasprepared.

Diethylene glycol diethyl ether, dipropylene glycol monomethyl ether,γ-butyrolactone, tetraethylene glycol dimethyl ether and a surfactant(BYK-UV3570, a product of BYK-Chemie, Japan), in amounts correspondingto the following wt % were introduced into a container, and mixed andstirred for 30 minutes using a magnetic stirrer to completely dissolve.A fixing resin (polyacryl polyol-type fixing resin: N-2043-AF-1 orN-2043-60MEX, a product of Harima Chemicals, Inc., polyurethane-typefixing resin: SANPRENE IB-501, a product of Sanyo Chemical Industries,Ltd., or vinyl chloride-vinyl acetate copolymer) were added to thecontainer, followed by mixing and stirring for 30 minutes. The pigmentdispersion obtained above was added to the container, followed by mixingand stirring for 1 hour. The resulting mixture was filtered using a 5 μmPTFE-made membrane filter to obtain each color ink composition.

Examples (1-1) to (1-5) and Comparative Examples (1-1) to (1-3) Example(1-1): Black Ink Composition 1

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt % Dipropylene glycol monomethylether 34.7 wt % Surfactant 0.2 wt % (BYK-UV3570, a product ofBYK-Chemie, Japan) Polyacryl polyol-type fixing resin 5 wt %(N-2043-AF-1, a product of Harima Chemicals, Inc.)

Example (1-2): Black Ink Composition 2

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 50.6 wt % Dipropylene glycol monomethylether 33.7 wt % Surfactant 0.2 wt % (BYK-UV3570, a product ofBYK-Chemie, Japan) Polyurethane-type fixing resin 7.5 wt % (SANPRENEIB-F370, a product of Sanyo Chemical Industries, Ltd.)

Example (1-3): Black Ink Composition 3

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 49.1 wt % Dipropylene glycol monomethylether 32.7 wt % Surfactant 0.2 wt % (BYK-UV3570, a product ofBYK-Chemie, Japan) Polyurethane-type fixing resin 10 wt % (SANPRENEIB-F501, a product of Sanyo Chemical Industries, Ltd.)

Comparative Example (1-1): Black Ink Composition 4

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 53.3 wt %   Dipropylene glycolmonomethyl ether 35.5 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Fixing resin 3 wt % (Vinyl chloride-vinylacetate copolymer)

Comparative Example (1-2): Black Ink Composition 5

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt %   Dipropylene glycolmonomethyl ether 34.7 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Ion-exchanged water 5 wt %

Comparative Example (1-3): Black Ink Composition 6

C.I. Pigment Black 7   5 wt % Dispersant (FLORENE DOPA-33)   3 wt %Diethylene glycol diethyl ether 55.1 wt % Dipropylene glycol monomethylether 36.7 wt % Surfactant  0.2 wt % (BYK-UV3570, a product ofBYK-Chemie, Japan)

Example (1-4): Black Ink Composition 7

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt %   Dipropylene glycolmonomethyl ether 34.7 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Polyacryl polyol-type fixing resin 5 wt %(N-2043-60MEX, a product of Harima Chemicals, Inc.)

Example (1-5): Black Ink Composition 8

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 53.8 wt %   γ-Butyrolactone 15 wt % Tetraethylene glycol dimethyl ether 18 wt %  Surfactant 0.2 wt %  (BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)

The following “printing evaluation 1” was conducted on Black InkCompositions 1 to 3, 7 and 8 of Examples (1-1) to (1-5) above and BlackInk Compositions 4 to 6 of Comparative Examples (1-1) to (1-3) above.

Printing Evaluation 1:

Using ink-jet printer SJ-540, a product of Roland D. G., Black InkCompositions 1 to 8 were charged in the respective black lines, andsolid image printing was conducted at a heating temperature of 50° C.Recording media used were a vinyl chloride sheet (Viewcal 900 (white), aproduct of Sakurai Co., Ltd.), an olefin sheet (Viewcal 2000 (white), aproduct of Sakurai Co., Ltd.), a PET film (PG-50L, a product of LamiCorporation Inc.), and a polycarbonate film (YUPIRON, a product ofMitsubishi Engineering-Plastics Corporation), all cut to an A4 size. Theevaluation results of fixability based on the following evaluation indexare shown in Table 1.

Fixability Evaluation Index

Tape Peel Test:

AA: Peeling is not generated at the interface between a cured coatingand a film.

A: A part of an edge part of a cured coating adheres to apressure-sensitive adhesive layer of a tape and peeled, but it is apractical level.

B: Peeling is generated at the interface between a cured coating and afilm, large part of a cured coating adheres to a pressure-sensitiveadhesive layer of a tape, and it is not a practical level.

C: Peeling is generated at the interface between a cured coating and afilm, and the whole cured coating adheres to a tape and peeled.

TABLE 1 Evaluation Result Viewcal Viewcal Ink composition 900 2000PG-50L FE-2000 Example (1-1) Black Ink Composition 1 AA AA AA AA Example(1-2) Black Ink Composition 2 AA AA A A Example (1-3) Black InkComposition 3 AA AA A A Example (1-4) Black Ink Composition 7 AA AA AAAA Example (1-5) Black Ink Composition 8 AA AA AA AA Comparative Example(1-1) Black Ink Composition 4 A A B B Comparative Example (1-2) BlackInk Composition 5 A A C C Comparative Example (1-3) Black InkComposition 6 A A C C

As is apparent from Table 1, a good printed matter having goodfixability is obtained with the oil-based ink composition of theinvention using an alkylene glycol compound as an organic solvent andhaving a resin emulsion added thereto.

Example (1-6)

Using the following color ink set (ink set comprising Yellow InkComposition 1, Magenta Ink Composition 1 or Cyan Ink Composition 1),full color image printing was carried out, and the following “printingevaluation 2” was conducted.

Yellow Ink Composition 1:

C.I. Pigment Yellow 155 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt %   Dipropylene glycolmonomethyl ether 34.7 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Polyacryl polyol-type fixing resin 5 wt %(N-2043-AF-1, a product of Harima Chemicals, Inc.)Magenta Ink Composition 1:

C.I. Pigment Violet 19 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt %   Dipropylene glycolmonomethyl ether 34.7 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Polyacryl polyol-type fixing resin 5 wt %(N-2043-AF-1, a product of Harima Chemicals, Inc.)Cyan Ink Composition 1:

C.I. Pigment Blue 15:3 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 52.1 wt %   Dipropylene glycolmonomethyl ether 34.7 wt %   Surfactant 0.2 wt %   (BYK-UV3570, aproduct of BYK-Chemie, Japan) Polyacryl polyol-type fixing resin 5 wt %(N-2043-AF-1, a product of Harima Chemicals, Inc.)

Example (1-7)

Using the following color ink set (ink set comprising Black InkComposition 9, Yellow Ink Composition 2, Magenta Ink Composition 2 orCyan Ink Composition 2), full color image printing was carried out, andthe following “printing evaluation 2” was conducted.

Black Ink Composition 9:

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.6 wt %   Surfactant 0.2 wt %  (BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Yellow Ink Composition 2:

C.I. Pigment Yellow 155 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.3 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.7 wt %   Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Magenta Ink Composition 2:

C.I. Pigment Violet 19 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.3 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.7 wt %   Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Cyan Ink Composition 2:

C.I. Pigment Blue 15:3 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.3 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.7 wt %   Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)

Example (1-8)

Using the following color ink set (ink set comprising Black InkComposition 9, Yellow Ink Composition 3, Magenta Ink Composition 3 orCyan Ink Composition 3), full color image printing was carried out, andthe following “printing evaluation 2” was conducted.

Black Ink Composition 9:

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.6 wt %   Surfactant 0.2 wt %  (BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Yellow Ink Composition 3:

C.I. Pigment Yellow 155 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.6 wt %   Surfactant 0.2 wt %  (BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Magenta Ink Composition 3:

C.I. Pigment Violet 19 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt %   γ-Butyrolactone 13 wt % Tetraethylene glycol dimethyl ether 15.6 wt %   Surfactant 0.2 wt %  (BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)Cyan Ink Composition 3:

C.I. Pigment Blue 15:3 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt % γ-Butyrolactone 13 wt %Tetraethylene glycol dimethyl ether 15.6 wt % Surfactant 0.2 wt %(BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)

Example (1-9)

Using the following color ink set (ink set comprising Black InkComposition 10, Yellow Ink Composition 4, Magenta Ink Composition 4 orCyan Ink Composition 4), full color image printing was carried out, andthe following “printing evaluation 2” was conducted.

Black Ink Composition 10:

C.I. Pigment Black 7 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt % γ-Butyrolactone 13 wt %Tetraethylene glycol dimethyl ether 15.6 wt % Surfactant 0.2 wt %(BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)Yellow Ink Composition 4:

C.I. Pigment Yellow 213 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt % γ-Butyrolactone 13 wt %Tetraethylene glycol dimethyl ether 15.6 wt % Surfactant 0.2 wt %(BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)Magenta Ink Composition 4:

C.I. Pigment Violet 19 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt % γ-Butyrolactone 13 wt %Tetraethylene glycol dimethyl ether 15.6 wt % Surfactant 0.2 wt %(BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)Cyan Ink Composition 4:

C.I. Pigment Blue 15:3 5 wt % Dispersant (FLORENE DOPA-33) 3 wt %Diethylene glycol diethyl ether 58.2 wt % γ-Butyrolactone 13 wt %Tetraethylene glycol dimethyl ether 15.6 wt % Surfactant 0.2 wt %(BYK-UV3570, a product of BYK-Chemie, Japan) Polyacryl polyol-typefixing resin 5 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)Printing Evaluation 2:

A color ink set comprising each ink composition (Examples (1-6) to(1-9)) was used. Using an ink-jet printer EM-930C, a product of SeikoEpson Corporation, each ink composition was charged in the respectivecorresponding color line, and full color image printing was carried outat ordinary temperature under ordinary pressure. The recording mediumused was a vinyl chloride sheet cut to A4 size (Viewcal 2000 (white), aproduct of Sakurai Co., Ltd.). After printing, a printed matter wasdried at ordinary temperature overnight.

As a result of the printing evaluation 2, high image quality and highdefinition full color image having excellent fixability was obtained.

Examples (2-1) to (2-5) and Comparative Examples (2-1) and (2-2)

Each white ink composition of the following Examples (2-1) to (2-5) andComparative Examples (2-1) and (2-2) was prepared as follows.

Preparation of Hollow Resin Emulsion 1:

(1) Polymer Particle 1

100 parts by weight of styrene, 1 part by weight of α-methylstyrenedimer, 14 parts by weight of t-dodecylmercaptane, 0.8 part by weight ofsodium dodecylbenzene sulfonate, 1.0 part by weight of potassiumpersulfate and 200 parts by weight of water were placed in a 2 litersreaction vessel, stirred in nitrogen gas, and heated to 80° C. toconduct emulsion polymerization for 6 hours. Polymer Particle 1 thusobtained had an average particle size of 250 nm.

(2) Hollow Resin Emulsion 1

10 parts by weight (in terms of solid content) of Polymer Particle 1obtained in (1) above, 0.3 part by weight of sodium laurylsulfate, 0.5part by weight of potassium persulfate and 400 parts by weight of waterwere placed in a reaction vessel. A crosslinking polymerizable monomercomposition comprising a mixture of 11.6 parts by weight ofdivinylbenzene (purity 55% by weight; the remainder is a monofunctionalvinyl monomer), 8.4 parts by weight of ethyl vinylbenzene, 5 parts byweight of methacrylic acid and 75 parts by weight of methyl methacrylatewere added to the reaction vessel. The resulting mixture was stirred at30° C. for 1 hour and further stirred at 70° C. for 5 hours to conductemulsion polymerization treatment, thereby obtaining an aqueousdispersion. As a result of measuring the dispersion obtained with aparticle size analyzer (Microtrack UPA: a product of Nikkiso Co., Ltd.),the particle size was 520 nm. Separately, as a result of observing thedispersion with a transmission electron microscope, it was confirmed tobe hollow resin fine particles. The emulsion thus obtained is calledHollow Resin Emulsion 1.

Preparation of Diethylene Glycol Diethyl Ether Dispersion A of HollowResin Emulsion 1:

The Hollow Resin Emulsion 1 obtained was separated from water bycentrifugal separation method, and then dried at 40° C. under reducedpressure for 3 days to further remove water. The Hollow Resin Emulsion 1obtained was weighed to a round-bottom flask, diethylene glycol diethylether was added to the flask such that a solid content concentration was20 wt %, and the resulting mixture was stirred using a magnetic stirrerfor 24 hours. Subsequently, the round-bottom flask containing adiethylene glycol diethyl ether dispersion of Hollow Resin Emulsion 1was placed in an ultrasonic cleaning tank, and vacuum devolatilizationtreatment was carried out with an aspirator for 8 hours while conductingultrasonic dispersion, thereby completely substituting air in the HollowResin Emulsion 1 with diethylene glycol diethyl ether. The dispersionobtained is called diethylene glycol diethyl ether dispersion A of theHollow Resin Emulsion 1.

Preparation of White Ink Composition 1 (Example (2-1))

Using the diethylene glycol diethyl ether dispersion A of the HollowResin Emulsion 1, White Ink Composition 1 having the followingcomposition was prepared.

Dipropylene glycol monomethyl ether and a surfactant were dispensed in avessel, and sufficiently mixed with a magnetic stirrer for 30 minutes.The resin emulsion N-2043-AF-1 was added to the vessel, and theresulting mixture was similarly stirred for 30 minutes to sufficientlymix. The dispersion A was added to the vessel, followed by stirring andmixing for 1 hour. A product obtained was filtered with a 10 μmPTFE-made membrane filter to obtain White Ink Composition 1 (Example(2-1)).

White Ink Composition 1: Example (2-1)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 60.0 wt% Dipropylene glycol monomethyl ether 20.8 wt % Surfactant 0.2 wt %(BYK-UV3500, a product of BYK-Chemie, Japan) Polyacryl polyol-type resinemulsion 4.0 wt % (N-2043-AF-1, a product of Harima Chemicals, Inc.)

The following White Ink Compositions 2 to 5 (Examples (2-2) to (2-5))and White Ink Compositions 4 and 5 (Comparative Examples (2-1) and(2-2)) were prepared in the same manner as in the White Ink Composition1 (Example (2-1)).

White Ink Composition 2: Example (2-2)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 60.0 wt% γ-Butyrolactone 11 wt % Tetraethylene glycol dimethyl ether 10.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan)Polyacryl polyol-type resin emulsion 3.0 wt % (N-2043-AF-1, a product ofHarima Chemicals, Inc.)

White Ink Composition 3: Example (2-3)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 60.0 wt% γ-Butyrolactone 10 wt % Tetraethylene glycol dimethyl ether 9.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan) Resinemulsion 3.0 wt % (SANPRENE IB-F370, a product of Sanyo ChemicalIndustries, Ltd.)

White Ink Composition 4: Comparative Example (2-1)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 62 wt %γ-Butyrolactone 11.5 wt % Tetraethylene glycol dimethyl ether 11.3 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan)

White Ink Composition 5: Comparative Example (2-2)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 62 wt %γ-Butyrolactone 10.5 wt % Tetraethylene glycol dimethyl ether 10.3 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan) Resin2.0 wt % (Cellulose acetate butyrate, degree of butylation: 50 to 54%, aproduct of Kanto Chemical Co., Inc.)

Comparative Examples (2-3) and (2-4) and Reference Example

Each white ink composition of the following Comparative Examples (2-3)and (2-4) and Reference Example was prepared as follows.

Preparation of Titanium Dioxide Fine Particles

Titanium-containing ore was dissolved with sulfuric acid to obtain atitanium sulfate solution. The titanium sulfate solution was hydrolyzedto obtain aqueous titanium oxide. 0.50 part by weight of ammoniumphosphate, 0.30 part by weight of potassium sulfate and 0.30 part byweight of aluminum sulfate were added to 100 parts of the aqueoustitanium oxide in terms of TiO₂. The aqueous titanium oxide was heatedin a laboratory rotating muffle furnace until a product temperaturereached 1,020° C. Titanium dioxide fine particles formed were cooled toroom temperature, and observed with a transmission electronmicrophotograph. As a result, it was found that the fine particles areanatase type particles having an average primary particle size of 0.13μm. 15 parts by weight of the titanium dioxide fine particles as asurface-treated white pigment, 5 parts by weight of apolyoxyalkylene-added polyalkylene amine (DISCOL N-518, a product ofDai-Ichi Kogyo Seiyaku Co., Ltd.) as a dispersant, and 80 parts byweight of diethylene glycol diethyl ether were mixed to obtain a slurry.Zirconia beads (1.0 mm diameter) in an amount of 1.5 times the amount ofthe slurry were charged, and dispersion was conducted for 2 hours with asand mill (a product of Yasukawa Electric Corporation). The beads wereremoved to obtain a monomer dispersion B containing 60 wt % of thetitanium dioxide fine particles. Using the monomer dispersion Bcontaining 60 wt % of the titanium dioxide fine particles, White InkComposition 6 (Comparative Example 3) was prepared with the followingcomposition. Specifically, diethylene glycol diethyl ether,γ-butyrolactone, tetraethylene glycol dimethyl ether and a surfactantwere dispensed in a vessel, and stirred and mixed for 30 minutes with amagnetic stirrer to sufficiently mix. 40 parts by weight of thedispersion B were added to the resulting mixture, followed by stirringand mixing for 1 hour. A product obtained was filtered using a 10 μmPTFE-made membrane filter to obtain White Ink Composition 6 (ComparativeExample (2-3)).

White Ink Compositions 7 (Comparative Example (2-4)) and 8 (ComparativeExample (2-5)) were prepared in the same manner as above.

White Ink Composition 6: Comparative Example (2-3)

Titanium dioxide fine particles 15.0 wt % Polyoxyalkylene-addedpolyalkylene amine 5.0 wt % (DISCOL N-518, a product of Dai-Ichi KogyoSeiyaku Co., Ltd.) Diethylene glycol diethyl ether 56 wt %γ-Butyrolactone 12 wt % Tetraethylene glycol dimethyl ether 11.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan)

White Ink Composition 7: Comparative Example (2-4)

Titanium dioxide fine particles 15.0 wt % Polyoxyalkylene-addedpolyalkylene amine 5.0 wt % (DISCOL N-518, a product of Dai-Ichi KogyoSeiyaku Co., Ltd.) Diethylene glycol diethyl ether 56.0 wt %γ-Butyrolactone 11 wt % Tetraethylene glycol dimethyl ether 10.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan) Resin2.0 wt % (Cellulose acetate butyrate, degree of butylation: 50 to 54%, aproduct of Kanto Chemical Co., Inc.)

White Ink Composition 8: Reference Example

Titanium dioxide fine particles 15.0 wt % Polyoxyalkylene-addedpolyalkylene amine 5.0 wt % (DISCOL N-518, a product of Dai-Ichi KogyoSeiyaku Co., Ltd.) Diethylene glycol diethyl ether 55.0 wt %γ-Butyrolactone 10 wt % Tetraethylene glycol dimethyl ether 9.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan)Polyacryl polyol-type resin emulsion 5.0 wt % (N-2043-AF-1, a product ofHarima Chemicals, Inc.)

Examples (2-4) and (2-5)

Each white ink composition of the following Examples (2-4) and (2-5) wasprepared as follows.

White Ink Composition 9: Example (2-4)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 60 wt %Dipropylene glycol monomethyl ether 20.8 wt % Surfactant 0.2 wt %(BYK-UV3500, a product of BYK-Chemie, Japan) Polyacryl polyol-type resinemulsion 3.0 wt % (N-2043-60MEX, a product of Harima Chemicals, Inc.)

White Ink Composition 10: Example (2-5)

Hollow Resin Emulsion 1 15 wt % Diethylene glycol diethyl ether 60 wt %γ-Butyrolactone 11 wt % Tetraethylene glycol dimethyl ether 10.8 wt %Surfactant 0.2 wt % (BYK-UV3500, a product of BYK-Chemie, Japan)Polyacryl polyol-type resin emulsion 3.0 wt % (N-2043-60MEX, a productof Harima Chemicals, Inc.)Printing Evaluation

Using an ink-jet printer SJ-540, a product of Roland D. G., Black InkComposition 1 was charged in a black line, and solid image printing wasconducted at a heating temperature of 50° C. Recording media used were aPET film (PG-50L, a product of Lami Corporation Inc.), and apolycarbonate film (YUPIRON, a product of MitsubishiEngineering-Plastics Corporation), all cut to an A4 size. Subsequently,White Ink Compositions 2 to 10 were successively charged in the blacklines, and printing evaluation was conducted.

Whiteness and Shielding Property Evaluation

The sample printed on the transparent recording medium in the printingevaluation was set on a black printed matter having OD value of 1.7, andL* value was measured using a spectrophotometer SPM-50, a product ofGRETAG-Macbeth. The L* value is an index of whiteness, and whiteness isexcellent as the value is large. Here, when a white sample is sandwichedbetween the black printed matter and the spectrophotometer, and the L*value is measured, a white printed sample shields the background blackprinted matter. As a result, whiteness and shielding property cansimultaneously be measured.

Press Life Test

Fixability Evaluation Index:

AA: Peeling of white pigment is not observed at all even when rubbedwith BEMCOT M-3 (a product of Asahi Kasei Corporation) twenty times.

A: Peeling of white pigment is not observed even when rubbed with BEMCOTM-3 ten times, but peeling is observed when rubbed with BEMCOT M-3twenty times.

B: Peeling of white pigment is observed when rubbed with BEMCOT M-3.

C: White pigment is wiped off from a recording medium to disappear whenrubbed with BEMCOT M-3.

Sedimentation Property Evaluation

Each of Ink Compositions 1 to 10 was dispensed in a 110 ml samplebottle, and allowed to stand for one week, and the state of the inkcomposition in the sample bottle was observed.

Index of Sedimentation Property Evaluation:

A: Precipitate is not observed at the bottom of the sample bottle.

B: Precipitate is observed at the bottom of the sample bottle, andtransparent portion is formed at the upper part of the ink composition.

C: White pigment is all precipitated on the bottom of the sample bottle,and a white pigment and an ink solvent are separated in two layers.

The evaluation results by the above evaluation methods are shown inTable 2 below.

TABLE 2 Evaluation of whiteness Ink Press life test Sedimentation andshielding property composition PG-50L FE-2000 property test (L* value)Example (2-1) White Ink 1 AA AA A 77 Example (2-2) White Ink 2 AA AA A78 Example (2-3) White Ink 3 A A A 74 Example (2-4) White Ink 9 AA AA A74 Example (2-5) White Ink 10 AA AA A 75 Comparative Example (2-1) WhiteInk 4 C C A 79 Comparative Example (2-2) White Ink 5 B B A 78Comparative Example (2-3) White Ink 6 C C C 70 Comparative Example (2-4)White Ink 7 B B B 66 Reference Example White Ink 8 A A C 68

As is apparent from Table 2, when an ink composition comprising amixture of a hollow resin emulsion, a resin emulsion and other additiveswas used (Examples (2-1) to (2-5)), good results were obtained in boththe press life test and the sedimentation property test.

Contrary to this, of the hollow resin emulsion and the resin emulsion,when the resin emulsion was not used (Comparative Examples (2-1) and(2-2)), good result was obtained in the sedimentation property test, butgood result was not obtained in the press life test. Furthermore, whenthe hollow resin emulsion and the resin emulsion were not used(Comparative Examples (2-3) and (2-4)), good results were not obtainedin both the press life test and the sedimentation property test. Whenthe emulsion resin was used, but the hollow resin emulsion was not used(Reference Example), the press life test was good, but good result wasnot obtained in the sedimentation property test.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

This application is based on Japanese Patent Application Nos.2007-010673 (filed Jan. 19, 2007), 2007-054383 (filed Mar. 5, 2007) and2007-271361 (filed Oct. 18, 2007), and the contents thereof are hereinincorporated by reference.

What is claimed is:
 1. An oil-based ink composition for ink-jetrecording comprising a coloring material, an organic solvent, anon-aqueous resin emulsion, and a silicone surfactant wherein theoil-based ink composition contains, as the organic solvent, at least oneof a diethylene glycol compound and a dipropylene glycol compound in acontent of 53.8% to 86.8% by weight based on the weight of the whole inkcomposition.
 2. The oil-based ink composition for ink-jet recording asclaimed in claim 1, wherein the resin constituting the non-aqueous resinemulsion is a polyacryl polyol resin.
 3. The oil-based ink compositionfor ink-jet recording as claimed in claim 1 or 2, wherein the dispersionmedium of the non-aqueous resin emulsion is an aliphatic hydrocarbonand/or an alicyclic hydrocarbon.
 4. The oil-based ink composition forink-jet recording as claimed in claim 3, wherein the aliphatichydrocarbon is a linear alkane and/or a branched alkane.
 5. Theoil-based ink composition for ink-jet recording as claimed in claim 3,wherein the alicyclic hydrocarbon is an alkyl cyclohexane.
 6. Theoil-based ink composition for ink-jet recording as claimed in claim 1,which is a white ink wherein the coloring material contains a hollowresin emulsion.
 7. An ink container containing the oil-based inkcomposition as claimed in claim
 1. 8. An ink-jet recording apparatusprovided with the oil-based ink composition as claimed in claim
 1. 9.The oil-based ink composition for ink-jet recording as claimed in claim1, wherein the silicone surfactant is a polyester-modified silicone or apolyether-modified silicone.